Threat assessments compile and analyze current and prospective challenges to a country’s security and interests, and may be conducted as part of wider reviews of national security and defence policy and institutions. They may serve as the basis for developing national security policy and strategy and for decisions on how to structure the institutions that implement security policy and strategy. This practice note describes processes behind the development of threat assessments and reviews, especially but not exclusively in countries emerging from conflict. It addresses the challenges of conducting reviews and assessments during ongoing conflict, examines the defence review process, and discusses the need to create procedures for periodic reviews of the security sector. The note does not specifically address assessment of public health threats or potential for natural disasters, but responding to such events may be a secondary role for national security services. This note discusses ways to ensure that results of threat assessments and reviews are accepted by national authorities and that the process itself is inclusive and legitimate.